Pistons and cylinder head after 43,000 miles of biofuels

[RustyCaddy]

Well the 1.5l head on the 1.6l block was getting some reservoir pressure again so i took it off today and am going to put on a 1.6liter head that has been waiting for like a year (because i am lazy).

This motor has been a DD and after 36000 of biodiesel at different blends (and about 7000 of straight vegetable oil) thought someone might be interested in the look of things.  Sorry, not the best pictures.


The carbon build up on the valves etc.


Cylinder 1 and 2 (see the reducer in the 1.6 blocks oil return for using the 1.5l head)


Cylinder 2,3 and 4 (you knew that)

Not a lot of coking really, but more than i would have expected with diesel.  i have wondered if the 25.3/1 (roughly) compression of the Franken might yield more complete combustion.  The cylinders look okay with little sign of wear from incomplete combustion.  There is some evidence of the crowns over heating below the pre-cup but i have kept the NA IP turned up to just below the black coal point so it has probably been getting hot but not major crown damage.  When i removed and pop tested the cylinder #2 injector when the Bosch nozzle was on, it was peeing and streaming and that cylinder looks the worst of all...so important to test injectors more often with veg oil i guess.  All and all it looks to have fared okay.

Hope the block isn't cracked

[burn_your_money]

Was the SVO waste or new? Was it heated? What outside temps was it run at? Proper startup/shutdown procedure? How long ago in the 43k did the SVO occur?

[RabbitJockey]

i don't understand what the oil drain reducer does?

[sprstu]

the 1.5 and 1.6 use a different diameter oil drain hole so in a franken build with a 1.6/1.5 you need to compensate or reduce.

[fatmobile]

Without that there the gasket wouldn't have metal on both sides to sandwich it.

[RustyCaddy]

Was the SVO waste or new? Was it heated? What outside temps was it run at? Proper startup/shutdown procedure? How long ago in the 43k did the SVO occur?

The vegetable oil was a mix of used and new...the new oil was mixed with the fryer oil to lower the acid value to between 4-6 KOH.  It was a two tank coolant heated system with a vegtherm near the IP.  The air temps varied from around 50 to 100deg. F depending on time of year and if i was working the swing shift or not; by mid-November began diluting the veg oil with biodiesel.  It ran very well using a 30/70 mix veg to bio using coolant heat only in mild Oregon late fall weather.  Used a looped return until swtching the 2nd tank over to biodiesel only at the end of December (so it was a heated biodiesel tank) and then switched (a manual switch) over to a return line to tank #2.  Coolant only heats the biodiesel in 30 degree weather to between 90-100 F.

The commute is about 30 miles each way so would run about 5 miles on biodiesel or diesel biodiesel blend (depending on the nighttime lows) to get the coolant temperature up before switching over.  The 3-way solenoid switch is normally off when the ignition isn't powered and a separate circuit wires a switch to the fuel 3-way solenoid, to power the vegtherm. Temps at the pump were between 160 and 190 F.  The vegtherm can be switched on/off but the vegtherm switch is de-energized whenever the switching solenoid for the vegetable oil feed line is off or the ignition is off (very important!).  Switch back to bio about 5 miles from home on the looped return.

Last ran straight vegetable oil about 2500 miles ago since then it has been between 30 and 0% veg oil.

Will finish cleaning the block, cylinder rims and piston crowns and post pics.

There is a tiny gap between the front of the oil return on the block and the head; even with the reducer it always seeped a little bit.

[Blocksmith]

Glad you posted this, but really interested in in-depth piston pics--from what I understand, that's where the potential problems occur when running WVO. Any coking / sticking of the piston rings?

[EcoTX]

Glad you posted this, but really interested in in-depth piston pics--from what I understand, that's where the potential problems occur when running WVO. Any coking / sticking of the piston rings?

Here's a thread with detailed pics of my tear down of an "alternative fuel experiment" motor.

Pretty similar results to this guy looks like, but would be nice to see more pictures.

I had to destroy the valve cover on mine prying it off as it was practically welded on with RTV stuff.

http://www.vwdiesel.net/forum/index.php?topic=32008.0

[RustyCaddy]

Glad you posted this, but really interested in in-depth piston pics--from what I understand, that's where the potential problems occur when running WVO. Any coking / sticking of the piston rings?

Not sure if i will pull the pistons.  Took the head off since i had to when the head gasket was beginning to fail and while at it to change out to the proper 1.6 liter head for the block.  Compression across all four pistons ranged between 390 to 410 with the engine cold; of course the head/block combo produced higher than normal compression.  Over time it was beating itself to death at 25.3 to 1 on a 11mm block. The engine started very, very easily...i'll miss that.